If you're a gamer, a trip to any arcade is sure to be a lot of fun. Mad jealous of their arcades. Also, Super Potato, obviously. Stuff tends to be a bit pricey but if you're into retro gaming at all, their stores are heaven. You can find anything there.
Last time I was in Osaka it was a public holiday so Dotonburi was super crowded but you can do some really cool shopping in the markets there. I'm a big fan of umeshu and Japanese whiskey in general and got me some good deals at Don Quijote. Also, Osaka Castle Park is kind of cool, if you've never been to any temples in Asia but when I went last time it was idiotically busy. You'll probably be OK, going this time of year though. Nishiki Market in Kyoto is a really cool food market too.
Otherwise, I agree with Evil. Asia is the kind of place you can just go to a subway stop in any major city, get off and explore. I'm not even one to really make big plans or a schedule or whatever. I was in Kyoto back in 2012 with some friends and fucked if I could even tell you where we went because I don't really pay much attention to the names of places, I just like to take it all in. I mostly go on holiday for the food, drinking and shopping tbh (first time I did Osaka and Kyoto with a bunch of good friends and we were ripped on good beer and whiskey for a lot of it). I might visit a few historic sites here and there but, and this is probably ignorant of me, if you've seen one temple, you've kind of seen them all IMHO. If those kinds of places aren't busy, they're worth a look but an absolute nightmare when everyone else is on holiday too.